1. Field of the Invention
The present invention relates to a drive means for the cutting station in a platen press, and in particular to a drive means for the cutting station in a platen press having a lower movable platen and an upper fixed platen with a means for actuating the lower movable platen.
2. Description of Prior Art
Drive devices for use in the cutting station of platen presses which operate by means of a driving cam and a group of toggle joints connected to the lower movable platen for actuating upward and downward movement of the platen are known in the art, such as those devices described, for example, in U.S. Pat. No. 1,053,566, U.S. Pat. No. 2,043,246, and U.S. Pat. No. 2,425,040.
U.S. Pat. No. 1,053,566 described the use of a cam mounted on a shaft outside of the toggle joint system. In this device, the movement generated by the cam is transferred to the toggle joint system by means of a lever equipped with cam followers.
U.S. Pat. No. 2,043,246 describes a drive means for a press having a cam on the access of symmetry of a toggle joint system. The cam is mounted on a shaft located beneath the lower pivot points of the toggle joints. A set of levers is connected at one end to a cam follower. A guide device is mounted on the axle carrying the cam follower for centering the system and determining the lateral position of the cam follower axle, so that forces are equally distributed to the toggle joints.
U.S. Pat. No. 2,425,040 also describes a drive means acting on the lower platen of a press. The device disclosed therein utilizes a cam having inner grooves for controlling motion of the lower platen. The movement generated by the cam is transferred to a stirrup linked by a lever to each toggle joint. Guiding of the lower platen is achieved by means of a central slide.
Each of the above devices permits variation in the stroke, speed and acelleration of the movement of the lower platen. Each of those devices, however, make use of one or more levers mounted between the toggle joints and the cams for transferring motion therebetween, which complicate the geometry of the driving device and increase the possibility of inaccurate movement because of the existence of a number of pivot points. Moreover, such structures exert substantial load on the contact surfaces between the cams and the cam followers, because the toggle joints are generally actuated in pairs by means of a single cam. Furthermore, none of the above devices has a security device which is capable of acting directly on the toggle joints in the event of a malfunction or a shutdown of the press.